Synthesis of novel 26-substituted milbemycin A4 derivatives and their acaricidal activities.

A series of novel 26-substituted milbemycin A4 derivatives was synthesized from 5-O-t-butyldimethylsilyl-26-hydroxymilbemycin A4 prepared by selenium dioxide oxidation of 5-O-t-butyldimethylsilyl-milbemycin A4. Their acaricidal activities were assessed against the organophosphorus-sensitive two-spotted spider mite (Tetranychus urticae) on the primary leaves of cowpea plants (Vigna sinesis Savi species) by spraying.